Weekly quiz: what kind of mark is this?
While sailing at night, you see this mark ahead.
Question of the day
🔹 What kind of mark is it?
And bonus questions
🔹 Can you describe its lighting pattern using the official description found on maps?
🔹 Where should you be heading?
👉 Reply on one of our social media below. We’ll post the solution right here next Sunday!
Identifying the correct mark
Thanks to all who have taken part in this quiz.
Lateral marks flash either red or green lights, and special marks exhibit yellow lights. Because the light is white, these possibilities are therefore eliminated.
The flashing sequence of the light can be described as 6 flashes every second, followed by a single longer flash. The period of the whole scheme is 15 seconds, after which it will repeat.
This excludes the possibility of isolated danger marks, whose distinctive white light rhythm consists of 2 quick flashes in intervals of either 5 or 10 seconds.
Safe water marks are a little trickier to disqualify, since they can display a variety of patterns of white light : either isophase (alternating on and off of equal lengths), occultation (longer periods of light than darkness), a single long flash every 10 seconds, or morse letter A (one short and one long flash).
Since none of these patterns match the sequence we observe, it’s probable we are dealing with a cardinal mark, so let’s have a look at those. A useful tip to remember is to think of these with a watch face in mind : east would be 3 o’clock, south 6, west 9, etc. The flash patterns of cardinal beacons have been designed to match these numbers. As can be seen in the diagram below, an east cardinal mark displays 3 flashes of light, and a west cardinal mark 9 flashes.
In the above diagram, we can identify our observed light sequence : 6 quick flashes and one long flash of white light. This matches a south cardinal mark.
In standardized shorthand, the pattern is described as : Q(6) + LFl. 15s.
Steering clear of danger
Based on the compass displayed at the bottom, we are heading just north of west. South is therefore to our left, and north to our right. A south cardinal mark is located south the danger area, and you should keep to its south. We therefore need to steer to port in order to stay in navigable waters. That is we should aim for a lower compass heading value.
Our next quiz on nautical charts is now live and awaiting your answer!
